How to Use Flutter Completers with a Backend on Back4app
Futures and Streams are the way to go in any type of asynchronous operation. However, sometimes both are not enough. If you want more advanced control over Futures, then use a Completer. It is a tool through which you can complete a Future programmatically. In a way, this provides better control over asynchronous operations. This tutorial will help you work through using Flutter Completers in an application that interacts with a backend on Back4app. By the end of this tutorial, you will have learned how to use Completers in a Flutter application to manage asynchronous tasks and integrate these tasks with a provided backend service from Back4app. We are going to create a very simple app which gets data back from a Back4app backend using a Completer for controlling the flow of the application.
To complete this tutorial, you will need:
- Flutter development environment set up on your local machine. Follow the Flutter installation guide if you haven't set it up yet.
- Basic knowledge of Dart and asynchronous programming in Flutter. If you need a refresher, check out the Flutter Async Programming Guide.
First, let's set up a simple backend on Back4app that our Flutter application will interact with.
- Log in to your Back4app account and create a new project.
- Set up a new Parse Class named Task, which will store tasks that our Flutter app will fetch. Add the following columns to the Task class:
- name (String): The name of the task.
- status (Boolean): The status of the task (completed or not).
- Add a few sample tasks in the Back4app database to test with. For example:
- Task 1: name = "Complete Flutter tutorial", status = true
- Task 2: name = "Start new project", status = false
Your Back4app backend is now ready to be accessed by the Flutter app.
Next, we'll create a new Flutter project.
- Open your terminal or command prompt.
- Run the following command to create a new Flutter project:
- Navigate to the project directory:
2. Open the project in your preferred code editor (e.g., VS Code, Android Studio).
Now, let's add the necessary dependencies to interact with Back4app.
- Open pubspec.yaml and add the following dependencies:
2. Run flutter pub get to install the dependencies.
3. In lib/main.dart, import the Parse SDK:
4. Initialize Parse in the main function:
Replace 'YOUR_APP_ID' and 'YOUR_CLIENT_KEY' with your actual Back4app credentials.
Now, let's use a Completer to fetch data from the Back4app backend and control when the data is available for use in the UI.
- In lib/main.dart, create a new class that will fetch tasks from Back4app using a Completer:
This class initializes a Completer, starts fetching data, and completes the Completer when the data is available.
2. In the MyApp widget, use the TaskManager to fetch and display tasks:
3. Run your Flutter app:
You should see a list of tasks fetched from your Back4app backend, with their names and completion status.
In this tutorial, you learned how to use Flutter Completers to manage asynchronous operations and control the flow of data fetching in your application. By integrating with Back4app, you created a simple yet powerful backend for your Flutter app, allowing you to fetch and display data dynamically. This approach can be extended to handle more complex scenarios, such as user authentication, data manipulation, and more.
For more information on using Flutter with Back4app, check out the Back4app Flutter documentation. Happy coding!
